Phased array antennas include multiple transmitting and/or receiving antenna elements that can be used together to form a directional radiation pattern. The relative phases or the respective signals feeding the antennas are controlled to create an effective radiation pattern that is strongest in a desired direction and suppressed in undesired directions. In this manner the antenna beam may be rapidly steered without any mechanical steering of the antenna (e.g., using a gimbal).
When quantized phase shifters are used to control the phases of the signals feeding the antenna elements, quantization errors result from the finite number of digitalization bits available to represent a signal phase. For example, in the case of a 2-bit phase shifter with four states, 0°, 90°, 180°, and 270°, the step size is 90° and the maximum quantization error is ±45°. When a radiating element requires a phase of 46°, the nearest state of this phase shifter is 90°, for which the error (between desired and actual) is 44°.
Quantization errors degrade antenna performance by increasing side lobe levels (SLL), i.e. the power density of side lobes that represent unwanted radiation in unwanted directions. Using a phase shifter with a greater number of quantization bits may improve antenna efficiency and lower SLLs, but it comes at the cost of a more expensive and complex phase shifter and control circuit.